A known electromagnetic actuator for an electromagnetic fuel injector includes a stator member, an armature member and an electromagnetic coil. The electromagnetic coil is energizable to flow magnetic flux through a designed magnetic circuit. The magnetic circuit includes the stator member and the armature member, and creates a magnetic force to move the armature member relative to the stator member. Some magnetic flux may short-circuit off of the designed magnetic circuit, for example through the coil, rather than through the armature member, resulting in magnetic flux leakage. It is believed that known electromagnetic actuators are designed to reduce magnetic flux leakage by using air gaps or non-magnetic materials to direct the magnetic flux through the designed magnetic circuit.
In the design of known actuators, the air gaps or non-magnetic materials have a minimum magnetic permeability, μ, assumed to be that of free space, μo, or 4π×10−7 Webers/amp-meter in SI units, which in Centimeter-Gram-Second units is the unity relative permeability value, μr=1. The maximum relative permeability in known designs is usually defined by the ferromagnetic components in the magnetic circuit, the value often being in the thousands. However, in known designs, a significant amount of useful magnetic flux is lost as magnetic flux leakage. It is believed that there is a need to reduce or eliminate this magnetic flux leakage.